U.S. patent number 10,673,385 [Application Number 16/040,594] was granted by the patent office on 2020-06-02 for supply modulator, modulated power supply circuit, and associated control method.
This patent grant is currently assigned to MEDIATEK INC.. The grantee listed for this patent is MEDIATEK Inc.. Invention is credited to Chien-Wei Kuan, Shih-Mei Lin, Che-Hao Meng, Da-Wei Sung.
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United States Patent |
10,673,385 |
Lin , et al. |
June 2, 2020 |
Supply modulator, modulated power supply circuit, and associated
control method
Abstract
A supply modulator, a modulated power supply circuit, and
associated control method are provided. The modulated power supply
circuit includes the supply modulator and a DC-DC voltage
converter, and the supply modulator includes a linear amplifier and
a switching converter. The linear amplifier generates an AC
component of a modulated voltage according to a regulated voltage
and an envelope tracking signal. The supply voltage is converted to
the regulated voltage by the DC-DC voltage converter, and the
regulated voltage is greater than or less than the supply voltage.
The switching converter includes a step-down circuit and a path
selection circuit. The path selection circuit selects one of the
supply voltage and the regulated voltage as a DC input voltage. The
step-down circuit converts the DC input voltage to a DC component
of the modulated voltage which is less than the DC input
voltage.
Inventors: |
Lin; Shih-Mei (Hsin-Chu,
TW), Meng; Che-Hao (Hsin-Chu, TW), Sung;
Da-Wei (Hsin-Chu, TW), Kuan; Chien-Wei (Hsin-Chu,
TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
MEDIATEK Inc. |
Hsin-Chu |
N/A |
TW |
|
|
Assignee: |
MEDIATEK INC. (Hsin-Chu,
TW)
|
Family
ID: |
66328956 |
Appl.
No.: |
16/040,594 |
Filed: |
July 20, 2018 |
Prior Publication Data
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Document
Identifier |
Publication Date |
|
US 20190140597 A1 |
May 9, 2019 |
|
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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62583069 |
Nov 8, 2017 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M
1/10 (20130101); H02M 3/33569 (20130101); H02M
3/1582 (20130101); H02M 3/158 (20130101); H03F
1/0227 (20130101); G05F 1/565 (20130101); H03F
2200/432 (20130101); H03F 1/0244 (20130101); H03F
3/217 (20130101); H03F 1/0211 (20130101); H02M
2001/007 (20130101); H03F 2200/102 (20130101) |
Current International
Class: |
H03F
3/217 (20060101); H02M 3/335 (20060101); G05F
1/565 (20060101); H03F 1/02 (20060101); H02M
3/158 (20060101) |
Field of
Search: |
;330/136,251,297 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Nguyen; Khanh V
Attorney, Agent or Firm: McClure, Qualey & Rodack,
LLP
Parent Case Text
This application claims the benefit of U.S. provisional application
Ser. No. 62/583,069, filed Nov. 8, 2017, the disclosure of which is
incorporated by reference herein in its entirety.
Claims
What is claimed is:
1. A supply modulator, configured for supplying a modulated voltage
to a power amplifier, comprising: a linear amplifier, electrically
connected to a direct current to direct current (DC-DC) voltage
converter, configured for generating an alternating current (AC)
component of the modulated voltage according to a regulated voltage
and an envelope tracking signal, wherein the DC-DC voltage
converter converts a supply voltage to the regulated voltage, and
the regulated voltage is greater than or less than the supply
voltage; and a switching converter, comprising: a step-down
circuit, electrically connected to the power amplifier, configured
for converting a direct current (DC) input voltage to a DC
component of the modulated voltage, wherein the DC component of the
modulated voltage is less than the DC input voltage; and a path
selection circuit, electrically connected to the DC-DC voltage
converter and the step-down circuit, configured for transmitting
one of the supply voltage and the regulated voltage which is
utilized as the DC input voltage to the step-down circuit.
2. The supply modulator according to claim 1, wherein the DC-DC
voltage converter comprises: a first inductor having a first
terminal and a second terminal; a first mode switch, electrically
connected to the first terminal, configured for receiving the
supply voltage; a second mode switch, electrically connected to the
first terminal and a ground terminal; a third mode switch,
electrically connected to the second terminal and the ground
terminal; a fourth mode switch, electrically connected to the
second terminal and the path selection circuit; and, a loading
capacitor, electrically connected to the fourth mode switch, the
ground terminal and the path selection circuit, wherein the
regulated voltage is related to switching statuses of the first
mode switch, the second mode switch, the third mode switch and the
fourth mode switch.
3. The supply modulator according to claim 2, wherein when the
regulated voltage is less than the supply voltage, the first mode
switch and the second mode switch are alternatively turned on, the
third mode switch is turned off, and the fourth mode switch is
turned on.
4. The supply modulator according to claim 2, wherein when the
regulated voltage is greater than the supply voltage, the first
mode switch is turned on, the second mode switch is turned off, and
the third mode switch and the fourth mode switch are alternatively
turned on.
5. The supply modulator according to claim 1, wherein the DC-DC
voltage converter and the supply modulator are electrically
connected to a voltage source configured for providing the supply
voltage, and the path selection circuit comprises: a first
selection switch, electrically connected to the voltage source and
the step-down circuit, configured for conducting the supply voltage
to the step-down circuit; and a second selection switch,
electrically conned between the DC-DC voltage converter and the
step-down circuit, configured for conducting the regulated voltage
to the step-down circuit, wherein one of the first selection switch
and the second selection switch is selected and switched on by a
path selection signal.
6. The supply modulator according to claim 5, wherein the step-down
circuit comprises: a second inductor, electrically connected to the
first selection switch and the second selection switch; and a
step-down switch, electrically connected to the first selection
switch, the second selection switch, the second inductor and a
ground terminal, wherein the one of the first selection switch and
the second selection switch being selected by the path selection
signal and the step-down switch are alternatively switched on.
7. The supply modulator according to claim 6, wherein the first
selection switch is a first PMOS transistor, the second selection
switch is a second PMOS transistor, and the step-down switch is an
NMOS transistor.
8. The supply modulator according to claim 7, wherein when the
first PMOS transistor is selected and turned on by the path
selection signal, the first PMOS transistor conducts the supply
voltage to the step-down circuit as the DC input voltage, and a
body terminal of the second PMOS transistor is conducted to one of
the supply voltage and the regulated voltage whichever has a
greater voltage level.
9. The supply modulator according to claim 7, wherein when the
second PMOS transistor is selected and turned on by the path
selection signal, the second PMOS transistor conducts the regulated
voltage to the step-down circuit as the DC input voltage, and a
body terminal of the first PMOS transistor is conducted to one of
the supply voltage and the regulated voltage whichever has a
greater voltage level.
10. The supply modulator according to claim 1, wherein the linear
amplifier is electrically connected to the power amplifier through
an output terminal, and the supply modulator further comprises: an
output capacitor, electrically connected to the output terminal and
a ground terminal, wherein the modulated voltage formed at the
output terminal comprises the AC component of the modulated voltage
and the DC component of the modulated voltage.
11. The supply modulator according to claim 1, wherein the supply
modulator further comprises: a coupling capacitor, electrically
connected to the linear amplifier and the power amplifier,
configured for providing a capacitor voltage difference.
12. The supply modulator according to claim 1, wherein the envelope
tracking signal is related to amplitude change of an input signal
being received by the power amplifier, and the power amplifier
operates based on the modulated voltage.
13. A modulated power supply circuit, configured for supplying a
modulated voltage to a power amplifier, wherein the modulated power
supply circuit comprises: a direct current to direct current
(DC-DC) converter, configured for converting a supply voltage to a
regulated voltage, wherein the regulated voltage is greater than or
less than the supply voltage; and a supply modulator, comprising: a
linear amplifier, electrically connected to the DC-DC voltage
converter, configured for generating an alternating current (AC)
component of the modulated voltage according to the regulated
voltage and an envelope tracking signal; and a switching converter,
comprising: a step-down circuit, electrically connected to the
power amplifier, configured for converting a direct current (DC)
input voltage to a DC component of the modulated voltage, wherein
the DC component of the modulated voltage is less than the DC input
voltage; and a path selection circuit, electrically connected to
the DC-DC voltage converter and the step-down circuit, configured
for transmitting one of the supply voltage and the regulated
voltage which is utilized as the DC input voltage to the step-down
circuit.
14. The modulated power supply circuit according to claim 13,
wherein the DC-DC voltage converter and the supply modulator are
electrically connected to a voltage source configured for providing
the supply voltage, and the path selection circuit comprises: a
first selection switch, electrically connected to the voltage
source and the step-down circuit, configured for conducting the
supply voltage to the step-down circuit; and a second selection
switch, electrically conned between the DC-DC voltage converter and
the step-down circuit, configured for conducting the regulated
voltage to the step-down circuit, wherein one of the first
selection switch and the second selection switch is selected and
switched on by a path selection signal.
15. The modulated power supply circuit according to claim 14,
wherein the step-down circuit comprises: a first inductor,
electrically connected to the first selection switch and the second
selection switch; and a step-down switch, electrically connected to
the first selection switch, the second selection switch, the first
inductor and a ground terminal, wherein the one of the first
selection switch and the second selection switch being selected by
the path selection signal and the step-down switch are
alternatively switched on.
16. The modulated power supply circuit according to claim 15,
wherein the first selection switch is a first PMOS transistor, the
second selection switch is a second PMOS transistor, and the
step-down switch is an NMOS transistor.
17. The modulated power supply circuit according to claim 16,
wherein when the first PMOS transistor is selected and turned on by
the path selection signal, the first PMOS transistor conducts the
supply voltage to the step-down circuit as the DC input voltage,
and a body terminal of the second PMOS transistor is conducted to
one of the supply voltage and the regulated voltage whichever has a
greater voltage level.
18. The modulated power supply circuit according to claim 16,
wherein when the second PMOS transistor is selected and turned on
by the path selection signal, the second PMOS transistor conducts
the regulated voltage to the step-down circuit as the DC input
voltage, and a body terminal of the first PMOS transistor is
conducted to one of the supply voltage and the regulated voltage
whichever has a greater voltage level.
19. The modulated power supply circuit according to claim 13,
wherein the envelope tracking signal is related to amplitude change
of an input signal being received by the power amplifier, and the
power amplifier operates based on the modulated voltage.
20. A control method of a modulated power supply circuit, wherein
the modulated power supply circuit supplies a modulated voltage to
a power amplifier, and the control method comprises steps of:
converting a supply voltage to a regulated voltage, wherein the
regulated voltage is greater than or less than the supply voltage;
generating an alternating current (AC) component of the modulated
voltage according to the regulated voltage and an envelope tracking
signal; utilizing one of the supply voltage and the regulated
voltage as a direct current (DC) input voltage; and converting the
DC input voltage to a DC component of the modulated voltage,
wherein the DC component of the modulated voltage is less than the
DC input voltage.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates in general to a supply modulator, a power
supply circuit, and an associated control method, and more
particularly to a supply modulator, a modulated power supply
circuit, and an associated control method for providing a modulated
voltage to a power amplifier.
Description of the Related Art
FIG. 1A (prior art) is a block diagram illustrating supplying a
supply voltage to a power amplifier based on a fix drain bias
approach. In FIG. 1A, the power amplifier (PA) 11 operates based on
a supply voltage Vdd having a constant DC value. After receiving an
input signal Sin, the power amplifier 11 amplifies the input signal
Sin to generate an amplified output signal Sout.
FIG. 1B (prior art) is a schematic diagram illustrating power
supplied to and consumed by the power amplifier based on the fixed
drain bias approach. The horizontal line Ln1 represents that the
supply voltage Vdd supplied to the power amplifier 11 is constant,
In FIG. 1B, the area shown with oblique lines (Ppa) represents
actual power consumption of the power amplifier 11, and the area
shown with dotted screentone (Pa1) represents the power which is
provided to but not utilized by the power amplifier 11, Therefore,
the area shown with dotted screentone (Pa1) implies the unnecessary
power loss in the power amplifier 11.
As shown in FIG. 1B, the fixed drain bias approach employs a fixed
supply voltage Vdd to the power amplifier 11, but the power
consumed by the power simplifier varies all the time. In
consequence, the fixed drain bias approach results in considerable
power loss and brings thermal issues.
The supply voltage Vdd is provided by a voltage source, typically a
battery. As the fixed drain bias approach is not power efficient,
battery life becomes shorter. Therefore, an efficient approach to
reduce unnecessary power dissipation is desired.
SUMMARY OF THE INVENTION
The invention is directed to a supply modulator, a modulated power
supply circuit, and an associated control method capable of
providing a modulated voltage to a power amplifier.
According to a first aspect of the present invention, a supply
modulator configured for supplying a modulated voltage to a power
amplifier is provided. The supply modulator includes a linear
amplifier and a switching converter. Being electrically connected
to a direct current to direct current (DC-DC) voltage converter,
the linear amplifier is configured for generating an alternating
current (AC) component of the modulated voltage according to a
regulated voltage and an envelope tracking signal. The DC-DC
voltage converter converts a supply voltage to the regulated
voltage, and the regulated voltage is greater than or less than the
supply voltage. The switching converter includes a step-down
circuit and a path selection circuit. The step-down circuit is
electrically connected to the power amplifier and configured for
converting a direct current (DC) input voltage to a DC component of
the modulated voltage. The DC component of the modulated voltage is
less than the DC input voltage. The path selection circuit is
electrically connected to the DC-DC voltage converter and the
step-down circuit and configured for transmitting one of the supply
voltage and the regulated voltage which is utilized as the DC input
voltage to the step-down circuit.
According to a second aspect of the present invention, a modulated
power supply circuit configured for supplying a modulated voltage
to a power amplifier is provided. The modulated power supply
circuit includes a direct current to direct current (DC-DC)
converter and a supply modulator. The DC-DC voltage converter is
configured for converting a supply voltage to a regulated voltage,
wherein the regulated voltage is greater than or less than the
supply voltage. The supply modulator includes a linear amplifier
and a switching converter, and the switching converter includes a
step-down circuit and a path selection circuit. Being electrically
connected to the DC-DC voltage converter, the linear amplifier is
configured for generating an alternating current (AC) component of
the modulated voltage according to the regulated voltage and an
envelope tracking signal. The step-down circuit is electrically
connected to the power amplifier and configured for converting a
direct current (DC) input voltage to a DC component of the
modulated voltage, The DC component of the modulated voltage is
less than the DC input voltage. The path selection circuit is
electrically connected to the DC-DC voltage converter and the
step-down circuit and configured for transmitting one of the supply
voltage and the regulated voltage which is utilized as the DC input
voltage to the step-down circuit.
According to a third aspect of the present invention, a control
method of a modulated power supply circuit is provided. The
modulated power supply circuit supplies a modulated voltage to a
power amplifier, and the control method includes following steps.
Firstly, a supply voltage is converted to a regulated voltage,
wherein the regulated voltage is greater than or less than the
supply voltage. Then, an alternating current (AC) component of the
modulated voltage is generated according to the regulated voltage
and an envelope tracking signal. Later, a supply voltage is
received, and one of the supply voltage and the regulated voltage
is utilized as a DC input voltage. Finally, the DC input voltage is
converted to a direct current (DC) component of the modulated
voltage. The DC component of the modulated voltage is less than the
DC input voltage.
The above and other aspects of the invention will become better
understood with regard to the following detailed description of the
preferred but non-limiting embodiment(s). The following description
is made with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A (prior art) is a block diagram illustrating supplying a
supply voltage to a power amplifier based on a fix drain bias
approach.
FIG. 1B (prior art) is a schematic diagram illustrating power
supplied to and consumed by the power amplifier based on the fixed
drain bias approach.
FIG. 2A is a block diagram illustrating a modulated power supply
circuit capable of supplying the modulated voltage Vpa to the power
amplifier according to the embodiment of the present
disclosure.
FIG. 2B is a schematic diagram illustrating power supplied to and
consumed by the power amplifier based on the envelope tracking bias
approach according to the embodiment of the present disclosure.
FIG. 3 is a schematic diagram illustrating internal blocks of the
modulated power supply circuit according to the embodiment of the
present disclosure.
FIG. 4 is a schematic diagram illustrating the DC-DC voltage
converter used in the modulated power supply circuit according to
the embodiment of the present disclosure.
FIG. 5A is a schematic diagram illustrating a step-down mode of the
DC-DC voltage converter.
FIG. 5B is a schematic diagram illustrating a step-up mode of the
DC-DC voltage converter.
FIG. 6 is a schematic waveform illustrating the switching control
signal Ssc1 for controlling the mode switches in the DC-DC voltage
converter.
FIG. 7A is a schematic diagram illustrating switching statuses of
the mode switches when the DC-DC voltage converter operates in the
step-down mode.
FIG. 7B is a schematic diagram illustrating switching statuses of
the mode switches when the DC-DC voltage converter operates in the
step-up mode.
FIG. 8 is a schematic diagram illustrating a configuration of the
modulated power supply circuit according to the embodiment of the
present disclosure.
FIG. 9 is a schematic diagram illustrating that the modulated power
supply circuit uses the AC coupling scheme.
FIG. 10 is a schematic diagram illustrating an implementation of
the selection circuit.
FIG. 11 is a schematic diagram illustrating the switching control
signal Ssc2 for controlling the step-down switch in the DC-DC
voltage converter.
FIG. 12A is a schematic diagram illustrating the configuration of
the switching converter when the regulated voltage Vm is less than
the supply voltage Vdd (Vm<Vdd) and when the supply voltage Vdd
is selected as the DC input voltage Vdc_in.
FIG. 12B is a schematic diagram illustrating the configuration of
the switching converter when the regulated voltage Vm is less than
the supply voltage Vdd (Vm<Vdd) and when the regulated voltage
Vm is selected as the DC input voltage Vdc_in.
FIG. 13A is a schematic diagram illustrating the configuration of
the switching converter when the regulated voltage Vm is greater
than the supply voltage Vdd (Vm>Vdd) and when the supply voltage
Vdd is selected as the DC input voltage Vdc_in.
FIG. 13B is a schematic diagram illustrating the configuration of
the switching converter when the regulated voltage Vm is greater
than the supply voltage Vdd (Vm>Vdd) and when the regulated
voltage Vm is selected as the DC input voltage Vdc_in.
DETAILED DESCRIPTION OF THE INVENTION
To improve the operating lifetime of the battery, an envelope
tracking (hereinafter, ET) power management approach is provided in
the present disclosure. Instead of providing a fixed supply voltage
Vdd to the power amplifier, a dynamically adjusted modulated
voltage Vpa is supplied to the power amplifier. As the modulated
voltage Vpa is varied by the envelope of the input signal Sin of
the power amplifier, the power loss can be significantly
reduced.
FIG. 2A is a block diagram illustrating a modulated power supply
circuit capable of supplying the modulated voltage Vpa to the power
amplifier according to the embodiment of the present disclosure. As
shown in FIG. 2A, the modulated power supply circuit 25 is
electrically connected to a voltage source 23, an envelope detector
22, and a power amplifier 21, and the envelope detector 22 is
electrically connected to the power amplifier 21. The power
amplifier 21 can be, for example, a class AB amplifier.
The voltage source 23 is configured for supplying a supply voltage
Vdd having a constant DC value, and the envelope detector 22 is
configured for detecting an envelope tracking signal Venv. The
envelope tracking signal Venv represents and/or carries envelope
information that is related to amplitude change of the input signal
Sin.
The modulated power supply circuit 25 is configured for supplying
the modulated voltage Vpa to the power amplifier 21. The modulated
power supply circuit 25 further includes a direct current to direct
current (DC-DC) voltage converter 26 and a supply modulator 28. The
DC-DC voltage converter 26 is configured for converting the supply
voltage Vdd to a regulated voltage Vm.
According to the embodiment of the present disclosure, the DC-DC
voltage converter 26 can be a boost converter or a buck converter.
Thus, the regulated voltage Vm can be greater than or less than the
supply voltage Vdd (that is, Vm>Vdd or Vm<Vdd). More details
about the DC-DC voltage converter 26 and the supply modulator 28
are illustrated below.
Similar to FIG. 1A, the power amplifier 21 receives the input
signal Sin and further amplifies the input signal Sin to generate
the amplified output signal Sout. However, instead of receiving the
supply voltage Vdd from the voltage source 23, the power amplifier
21 in FIG. 2A receives the modulated voltage Vpa from the modulated
power supply circuit 25. Then, the power amplifier 21 operates
based on the modulated voltage Vpa.
FIG. 2B is a schematic diagram illustrating power supplied to and
consumed by the power amplifier based on the envelope tracking bias
approach according to the embodiment of the present disclosure. The
curve Ln2 represents the modulated voltage Vpa supplied to the
power amplifier 21, the area shown with oblique lines (Ppa)
represents actual power consumption of the power amplifier 21, and
the area shown with dotted screentone (Pa2) represents the
unnecessary power loss in the power amplifier 21.
Please refer to FIGS. 1B and 2B together. In FIGS. 1B and 2B, sizes
of the areas shown with oblique lines (Ppa) are equivalent, but the
sizes of the areas shown with dotted screentone (Pa1, Pa2) are
different. As the modulated voltage Vpa being generated at an
output terminal Npa of the modulated power supply circuit 25 should
have a similar tendency of the input signal Sin, the area with
dotted screentone shown in FIG. 2B is much smaller than that in
FIG. 1B (Pa2<<Pa1). Therefore, by providing the time-variant
power to the power amplifier 21, the power utilization of the
modulated power supply circuit 25 becomes more efficient, and the
amount of power waste can be reduced.
FIG. 3 is a schematic diagram illustrating internal blocks of the
modulated power supply circuit according to the embodiment of the
present disclosure. The modulated power supply circuit 25 includes
a DC-DC voltage converter 26 and a supply modulator 28. The supply
modulator 28 includes a switching converter 281 and a linear
amplifier 283, and the switching converter 281 further includes a
selection circuit 281a and a step-down circuit 281b.
The linear amplifier 283 is electrically connected to the DC-DC
voltage converter 26 and the power amplifier 21. The step-down
circuit 281b is electrically connected to the power amplifier 21,
and the path selection circuit 281a is electrically connected
between the DC-DC voltage converter 26 and the step-down circuit
281b.
According to the embodiment of the present disclosure, the
modulated voltage Vpa provided by the modulated power supply
circuit 25 includes a DC component (Vpa_dc) and an AC component
(Vpa_ac). The switching converter 281 is configured for providing
the DC component of the modulated voltage Vpa_dc, and the linear
amplifier 283 is configured for providing the AC component of the
modulated voltage Vpa_ac.
The modulated power supply circuit 25 can jointly operate with a
control circuit 20. The control circuit 20 concerns the usage
environment of the portable device, selects suitable settings
related to the power amplifier and determines how operations of the
modulated power supply circuit 25 should be adjusted.
For example, the control circuit 20 may generate and transmit
switching control signals Ssc1 , Ssc2 and a path selection signal
Spath to the modulated power supply circuit 25. A switching control
signal Ssc1 is transmitted to the DC-DC voltage converter 26, and
another switching control signal Ssc2 is transmitted to the path
selection circuit 281a and the step-down circuit 281b. The path
selection signal Spath is transmitted to the path selection circuit
281a.
As shown in FIG. 3, the linear amplifier 283 receives the regulated
voltage Vm from the DC-DC voltage converter 26. Moreover, the
linear amplifier 283 receives the envelope tracking signal Venv.
The regulated voltage Vm is utilized by the linear amplifier 283 as
its operation voltage, and the envelope tracking signal Venv is
further amplified to generate the AC component of the modulated
voltage Vpa_ac. Since the regulated voltage Vm is time-variant, the
operation voltage of the linear amplifier 283 also changes with
time.
The path selection circuit 281a can be, for example, a switch.
Being controlled by a path selection signal Spath, the path
selection circuit 281a may conduct the regulated voltage Vm from
the DC-DC voltage converter 26 to the step-down circuit 281b, or
conduct the supply voltage Vdd from the voltage source 23 to the
step-down circuit 281b. Thus, the step-down circuit 281b receives
one of the supply voltage Vdd and the regulated voltage Vm as its
input voltage. For the sake of illustration, the input voltage
received by the switching converter 281 can be defined as a DC
input voltage Vdc_in.
Then, the step-down circuit 281b converts the DC input voltage
Vdc_in to the DC component of the modulated voltage Vpa_dc. The DC
component of the modulated voltage Vpa_dc is less than the DC input
voltage Vdc_in.
As illustrated above, the DC-DC voltage converter receives the
supply voltage Vdd from the voltage source 23 and converts the
supply voltage Vdd to the regulated voltage Vm. Moreover, the
regulated voltage Vm can be greater than or less than the supply
voltage Vdd. Details about how the DC-DC voltage converter 26
operates are illustrated in FIGS. 4, 5A, 5B, 6, 7A and 7B.
FIG. 4 is a schematic diagram illustrating the DC-DC voltage
converter used in the modulated power supply circuit according to
the embodiment of the present disclosure. The DC-DC voltage
converter 26 includes four mode switches sw1, sw2, sw3, sw4, an
inductor L1 and a loading capacitor Cld. The switching statues of
the mode switches sw1, sw2, sw3, sw4 are controlled by the
switching control signal Ssc1 and dynamically adjusted, depending
on the operation mode of the DC-DC voltage converter 26.
For normal operation of the portable device, the DC-DC voltage
converter is usually preferred to operate as the buck converter.
Under such circumstances, operations of the DC-DC voltage converter
26 are discussed in FIGS. 5A and 7A.
Occasionally, when the battery is low or when high power UE support
is required, the DC-DC voltage converter is desired to operate as
the boost converter. Under such circumstances, operations of the
DC-DC voltage converter 26 are discussed in FIGS. 5B and 7B.
FIG. 5A is a schematic diagram illustrating a step-down mode of the
DC-DC voltage converter. When the DC-DC voltage converter 26
operates in the step-down mode as a buck converter, the regulated
voltage Vm is less than the supply voltage Vdd. Meanwhile, the mode
switches sw1, sw2 are alternatively switched on (toggled), the mode
switch sw3 remains OFF, and the mode switch sw4 remains ON.
Switching statuses of the mode switches sw1, sw2, sw3, sw4 when the
DC-DC voltage converter operates in the step-down mode are shown in
FIG. 7A.
FIG. 5B is a schematic diagram illustrating a step-up mode of the
DC-DC voltage converter. When the DC-DC voltage converter 26
operates in the step-up mode as a boost converter, the regulated
voltage Vm is greater than the supply voltage Vdd. Meanwhile, the
mode switch sw1 remains ON, the mode switch sw2 remains OFF, and
the mode switches sw3, sw4 are alternatively switched on (toggled).
Switching statuses of the mode switches sw1, sw2, sw3, sw4 when the
DC-DC voltage converter operates in the step-up mode are shown in
FIG. 7B.
FIG. 6 is a schematic waveform illustrating the switching control
signal Ssc1 for controlling the mode switches in the DC-DC voltage
converter. The period of the switching control signal Ssc1 is
represented as T1. The switching control signal Ssc1 is at a high
level during a pulse duration D1, and the switching control signal
Ssc1 is at a low level during a non-pulse duration (T1-D1).
FIG. 7A is a schematic diagram illustrating switching statuses of
the mode switches when the DC-DC voltage converter operates in the
step-down mode. In a case that the DC-DC voltage converter 26
operates in the step-down mode, the upper part of FIG. 7A shows
that the mode switch sw1 is turned on, and the mode switch sw2 is
turned off if the switching control signal Ssc1 is at the high
level during the pulse duration D1, and the mode switch sw1 is
turned off, and the lower part of FIG. 6A shows that the mode
switch sw2 is turned on if the switching control signal Ssc1 is at
the low level during the non-pulse duration (T1-D1).
FIG. 7B is a schematic diagram illustrating switching statuses of
the mode switches when the DC-DC voltage converter operates in the
step-up mode. In a case that the DC-DC voltage converter 26
operates in the step-up mode, the upper part of FIG. 7B shows that
the mode switch sw3 is turned on, and the mode switch sw4 is turned
off if the switching control signal Ssc1 is at the high level
during the pulse duration D1, and the lower part of FIG. 7B shows
that the mode switch sw3 is turned off, and the mode switch sw4 is
turned on if the switching control signal Ssc1 is at the low level
during the non-pulse duration (T1-D1).
FIG. 8 is a schematic diagram illustrating a configuration of the
modulated power supply circuit according to the embodiment of the
present disclosure. The modulated power supply circuit 35 includes
a DC-DC voltage converter 36 and a supply modulator 38. The supply
modulator 38 includes a linear amplifier 383, a switching converter
381 and an output capacitor Cout. The switching converter 381
further includes a selection circuit 381a and a step-down circuit
381b. The output capacitor Cout is electrically connected to the
output terminal Npa and the ground terminal Gnd.
The selection circuit 381a includes two selection switches sw_u1,
sw_u2, which are controlled by the switching control signal Ssc2.
The selection switch sw_u1 is electrically connected between the
DC-DC voltage converter 36 and the step-down circuit 381b, and the
selection switch u2 is electrically connected between the voltage
source 33 and the step-down circuit 381b.
As illustrated above, the input voltage of the switching converter
381 is defined as the DC input voltage Vdc_in, which can be
selected from one of the supply voltage Vdd and the regulated
voltage Vm. When the switching control signal Ssc2 turns on the
selection switch sw_u1, the supply voltage Vdd is considered as the
DC input voltage Vdc_in of the switching converter 381. When the
switching control signal Ssc2 turns on the selection switch sw_u2,
the regulated voltage Vm is considered as the DC input voltage
Vdc_in of the switching converter 381.
According to the embodiment of the present disclosure, the
step-down circuit 381b performs a step-down function. In other
words, the output voltage of the switching converter 381, that is,
the DC component of the modulated voltage Vpa_dc is less than the
DC input voltage Vdc_in. The step-down circuit 381b includes an
inductor L2 and a step-down switch swd. The step-down switch swd is
selectively turned on, depending on the voltage level of the
switching control signal Ssc2. Details about how the DC-DC voltage
converter 26 operates are illustrated in FIGS. 10, 11, 12A, 12B,
13A and 13B.
In the modulated power supply circuits 35, 45 , the efficiencies of
the DC-DC voltage converters 36, 46 are better than the
efficiencies of the linear amplifiers 383, 483. Thus, it is
preferred to use the DC-DC voltage converters 36, 46 to provide the
majority of the modulated voltage Vpa. In addition, the voltage
level of the AC component of the modulated voltage Vpa_ac is better
to be lowered. Therefore, an AC-coupling scheme shown in FIG. 9 is
proposed to reduce the power consumption of the linear amplifier
383.
FIG. 9 is a schematic diagram illustrating that the modulated power
supply circuit uses the AC coupling scheme. The modulated power
supply circuit 45 includes a DC-DC voltage converter 46 and a
supply modulator 48. The supply modulator 48 includes a linear
amplifier 483, a switching converter 481, and a coupling capacitor
Ccp. Unlike the output capacitor Cout, the coupling capacitor Ccp
is electrically connected between the linear amplifier 483 and the
output terminal Nap.
The switching converter 481 includes a selection circuit 481a and a
step-down circuit 481b. The selection circuit 481a further includes
selections switches sw_u1, sw_u2, and the step-down circuit 481
further includes an inductor L2 and a step-down switch swd.
Operations of the switching converter 481 are similar to those of
the switching converter 381, and details are not redundantly
illustrated.
When the AC coupling scheme is used, the output terminal of the
linear amplifier 483 is electrically connected to the negative
terminal (-) of the coupling capacitor Ccp. This implies that a
capacitor voltage difference .DELTA.V exists between the two
terminals of the coupling capacitor Ccp, and swing of the output of
the linear amplifier 483 can be suppressed. Accordingly, the output
power of the linear amplifier 483 can be reduced, so as the total
power consumption of the modulated power supply circuit 45.
If the original variation range of the swing of the AC signal is
3V.about.5V, and if use of the coupling capacitor Ccp allows the
variation range of the swing of the AC component of the modulated
voltage Vpa_ac to be decreased to 1V.about.3V, the swing of the
output of the linear amplifier 483 (FIG. 9) is much smaller than
that of the linear amplifier 383 (FIG. 8). Based on the AC coupling
scheme, the power required by the linear amplifier 483 becomes
less, and efficiency of the modulated power supply circuit 45
becomes better.
FIG. 10 is a schematic diagram illustrating an implementation of
the selection circuit. The modulated power supply circuit 57
includes a DC-DC voltage converter 56, a linear amplifier 583, a
switching converter 58, and a coupling capacitor Ccp.
The switching converter 58 includes selections switches s_u1,
sw_u2, a step-down switch swd, an inductor L2, and a control switch
sw_c. In FIG. 10, the selection switch sw_u1 is assumed to be a
PMOS transistor M1, and the selection switch sw_u2 is assumed to be
another PMOS transistor M2. The step-down switch swd is assumed to
be an NMOS transistor M3.
In FIG. 10, the control switch sw_c is electrically connected to
the control circuit to receive a complementary switching control
signal Ssc2'. The complementary switching control signal Ssc2' has
an opposite logic level of the switching control signal Ssc2.
Switching status of the control switch sw_c is controlled by the
path selection signal Spath, The path selection signal Spath may be
used to conduct the complementary switching control signal Ssc2' to
the transistor M2 or to the transistor M1.
The source terminal of transistor M1 is electrically connected to
the voltage source 53 for receiving the supply voltage Vdd. The
source terminal of transistor M2 is electrically connected to the
DC-DC voltage converter 56 for receiving the regulated voltage Vm.
The drain terminals of the transistors M1, M2, M3 are electrically
connected together. The gate terminal of the transistor M3 is
electrically connected to the control circuit to receive the
complementary switching control signal Ssw2'. The gate terminals of
the transistors M1, M3 are selectively electrically connected to
the control circuit to receive the complementary switching control
circuit Ssw2'. According to the embodiment of the present
disclosure, connections of the body terminals of the transistor M1,
M2 are related to several parameters, for example, voltage levels
of the supply voltage Vdd and the regulated voltage Vm, which of
the supply voltage Vdd and the regulated voltage Vm is selected as
the DC input voltage Vdc_in, and so forth.
In FIG. 10, only one of the transistors M1, M2 is turned on at the
same time. When the path selection signal Spath selects to conduct
the complementary switching control signal Ssc2' to the transistor
M1, the transistor M1 is turned on and the supply voltage Vdd is
considered as the DC input voltage Vdc_in. When the path selection
signal Spath selects to conduct the complementary switching control
signal Ssc2' to the transistor M2, the transistor M2 is turned on
and the regulated voltage Vm is considered as the DC input voltage
Vdc_in.
FIG. 11 is a schematic diagram illustrating the switching control
signal Ssc2 for controlling the step-down switch in the DC-DC
voltage converter The period of the switching control signal Ssc2
is represented as T2. The switching control signal Ssc2 is at a
high level during the pulse duration D2, and the switching control
signal Ssc2 is at a low level during the non-pulse duration
(T1-D2).
In some applications, the power amplifier may need to support high
power user equipment (UE), and the modulated voltage Vpa higher
than the battery can support may be required. Under such
circumstance, the DC input voltage Vdc_in must be greater than the
supply voltage Vdd. Otherwise, the DC component of the modulated
voltage Vpa_dc is not enough. According to the embodiment of the
present disclosure, the switching control signals Ssc1, Ssc2, and
the DC input voltage Vdc_in can be freely adjusted by the control
circuit to support various requirements of different applications
of the power amplifier. Details about how connections of the body
terminals of the transistors M1, M2 are adjusted in response to
different settings of the switching control signal Ssc2 and the DC
input voltage Vdc_in are illustrated in FIGS. 12A, 12B, 13A, and
13B.
FIG. 12A is a schematic diagram illustrating the configuration of
the switching converter when the regulated voltage Vm is less than
the supply voltage Vdd (Vm<Vdd) and when the supply voltage Vdd
is selected as the DC input voltage Vdc_in. Table 1 is a table
listing the switching statues and connections of the body terminals
of transistors M1, M2, M3 shown in FIG. 12A. The first row is
corresponding to the upper part of FIG. 12A and the second row is
corresponding to the lower part of FIG. 12A.
TABLE-US-00001 TABLE 1 transistor M1 transistor M2 transistor M3
switching body switching body switching duration status terminal
status terminal status D2 ON Vdd OFF Vdd OFF T2-D2 OFF ON
When the supply voltage Vdd is selected as the DC input voltage
Vdc_in, the transistor M2 remains to be turned off, regardless of
changes of the switching control signal Ssc2. On the other hand,
the transistors M1, M3 are selectively turned on, depending on the
voltage level of the switching control signal Ssc2.
The upper part of FIG. 12A shows that the transistor M1 is turned
on, and the transistor M3 is turned off when the switching control
signal Ssc2 is at the high level (Ssc2'=L, pulse duration D2). The
lower part of FIG. 12A shows that the transistor M1 is turned off,
and the transistor M3 is turned on when the switching control
signal Ssc2 is at the low level (Ssc2'=H, non-pulse duration
(T2-D2)).
As the regulated voltage Vm in FIG. 12A is assumed to be less than
the supply voltage Vdd, the body terminal of the transistor which
remains to be turned off (that is, transistors M2 as shown in the
upper part and the lower part of FIG. 12A) are biased at the supply
voltage Vdd to ensure that no leakage current is generated at the
transistor M2. Therefore, in FIG. 12A, body terminals of the
transistors M1, M2 are biased at the supply voltage Vdd.
FIG. 12B is a schematic diagram illustrating the configuration of
the switching converter when the regulated voltage Vm is less than
the supply voltage Vdd (Vm<Vdd) and when the regulated voltage
Vm is selected as the DC input voltage Vdc_in, Table 2 is a table
listing the switching statuses and connections of the transistors
M1, M2, M3 shown in FIG. 12B. The first row is corresponding to the
upper part of FIG. 12B and the second row is corresponding to the
lower part of FIG. 12B.
TABLE-US-00002 TABLE 2 transistor M1 transistor M2 transistor M3
switching body switching body switching duration status terminal
status terminal status D2 OFF Vm ON Vm OFF T2-D2 OFF ON
When the regulated voltage Vm is selected as the DC input voltage
Vdc_in, the transistor M1 remains to be turned off, regardless of
changes of the switching control signal Ssc2. On the other hand,
the transistors M2, M3 are alternately turned on, depending on the
voltage level of the switching control signal Ssc2.
The upper part of FIG. 12B shows that the transistor M2 is turned
on and the transistor M3 is turned off when the switching control
signal Ssc2 is at the high level (Ssc2'=L, pulse duration D2). The
lower part of FIG. 12B shows that the transistor M2 is turned off
and the transistor M3 is turned on when the switching control
signal Ssc2 is at the low level (Ssc2'=H, non-pulse duration
(T2-D2)).
As the regulated voltage Vm in FIG. 12B is assumed to be less than
the supply voltage Vdd, the body terminal of the transistor which
remains to be turned off (that is, transistor M1 as shown in the
upper part and the lower part of FIG. 12B) are biased at the supply
voltage Vdd to ensure that no leakage current is generated at the
transistors M1. Therefore, in FIG. 12B, body terminals of the
transistors M1 are biased at the supply voltage Vdd while body
terminals of the transistors M2 are biased at the regulated voltage
Vm.
FIG. 13A is a schematic diagram illustrating the configuration of
the step-up converter when the regulated voltage Vm is greater than
the supply voltage Vdd (Vm>Vdd) and when the supply voltage Vdd
is selected as the DC input voltage Vdc_in. Table 3 is a table
listing the connection statuses shown in FIG. 13A. The first row is
corresponding to the upper part of FIG. 13A and the second row is
corresponding to the lower part of FIG. 13A.
TABLE-US-00003 TABLE 3 transistor M1 transistor M2 transistor M3
switching body switching body switching duration status terminal
status terminal status D2 ON Vdd OFF Vm OFF T2-D2 OFF ON
When the supply voltage Vdd is selected as the DC input voltage
Vdc_in, the transistor M2 remains to be turned off, regardless of
changes of the switching control signal Ssc2. On the other hand,
the transistors M1, M3 are selectively turned on, depending on the
voltage level of the switching control signal Ssc2.
The upper part of FIG. 13A shows that the transistor M1 is turned
on, and the transistor M3 is turned off when the switching control
signal Ssc2 is at the high level (Ssc2'=L, pulse duration D2). The
lower part of FIG. 13A shows that the transistor M1 is turned off,
and the transistor M3 is turned on when the switching control
signal Ssc2 is at the low level (Ssc2'=H, non-pulse duration
(T2-D2)).
As the regulated voltage Vm in FIG. 13A is assumed to be greater
than the supply voltage Vdd, the body terminal of the transistor
which remains to be turned off (that is, transistors M2 as shown in
the upper part and the lower part of FIG. 13A) are biased at the
regulated voltage Vm to ensure that no leakage current is generated
at the transistors M2. Therefore, in FIG. 13A, body terminals of
the transistors M1 are biased at the supply voltage Vdd while body
terminals of the transistors M2 are biased at the regulated voltage
Vm.
FIG. 13B is a schematic diagram illustrating the configuration of
the step-up converter when the regulated voltage Vm is greater than
the supply voltage Vdd (Vm>Vdd) and when the regulated voltage
Vm is selected as the DC input voltage Vdc_in. Table 4 is a table
listing the connection statuses shown in FIG. 13B. The first row is
corresponding to the upper part of FIG. 13B and the second row is
corresponding to the lower part of FIG. 13B.
TABLE-US-00004 TABLE 4 transistor M1 transistor M2 transistor M3
switching body switching body switching duration status terminal
status terminal status D2 OFF Vdd ON Vm OFF T2-D2 OFF ON
When the regulated voltage Vm is selected as the DC input voltage
Vdc_in, the transistor M1 remains to be turned off, regardless of
changes of the switching control signal Ssc2. On the other hand,
the transistors M2, M3 are alternately turned on, depending on the
voltage level of the switching control signal Ssc2.
The upper part of FIG. 13B shows that the transistor M2 is turned
on and the transistor M3 is turned off when the switching control
signal Ssc2 is at the high level (Ssc2'=L, pulse duration D2). The
lower part of FIG. 13B shows that the transistor M1 is turned off
and the transistor M3 is turned on when the switching control
signal Ssc2 is at the low level (Ssc2'=H, non-pulse duration
(T2-D2)).
As the regulated voltage Vm in FIG. 13B is assumed to be greater
than the supply voltage Vdd, the body terminal of the transistor
which remains to be turned off (that is, transistors M1 as shown in
the upper part and the lower part of FIG. 13B) are biased at the
regulated voltage Vm to ensure that no leakage current is generated
at the transistor M1. Therefore, in FIG. 13B, body terminals of the
transistors Ml, M2 are biased at the regulated voltage Vm.
Please refer to FIGS. 12A and 13A together. In a case that the
supply voltage Vdd is selected as the DC input voltage Vdc_in, the
body terminal of the transistor M1 is connected to receive the
supply voltage Vdd, while the connection of the body terminal of
the transistor M2 is not fixed but dependent on a comparison
between the supply voltage Vdd and the regulated voltage Vm.
Although transistors M2 in both FIGS. 12A and 13A remain to be
turned off, connections of the transistors M2 in these figures are
not completely identical.
When the supply voltage Vdd is greater than the regulated voltage
Vm, the body terminal of the transistor M2 receives the supply
voltage Vdd (FIG. 12A). When the supply voltage Vdd is less than
the regulated voltage Vm, the body terminal of the transistor M2
receives the regulated voltage Vm (FIG. 13A). Alternatively
speaking, the body terminal of the transistor M2 which remains to
be turned off when the supply voltage Vdd is considered as the DC
input voltage Vdc_in is electrically connected to whichever of the
supply voltage Vdd and the regulated voltage Vm having the greater
voltage level.
Please refer to FIGS. 12B and 13B together. In a case that the
regulated voltage Vm is selected as the DC input voltage Vdc_in,
the body terminal of the transistor M2 is connected to receive the
regulated voltage Vm, while the connection of the body terminal of
the transistor M1 is not fixed but dependent on a comparison
between the supply voltage Vdd and the regulated voltage Vm. The
transistors M1 in both FIGS. 12B and 13B remain to be turned off,
but connections of the transistors M1 in these figures are not
completely identical.
When the supply voltage Vdd is greater than the regulated voltage
Vm, the body terminal of the transistor M1 receives the supply
voltage Vdd (FIG. 12B). When the supply voltage Vdd is less than
the regulated voltage Vm, the body terminal of the transistor M2
receives the regulated voltage Vm (FIG. 13B). Alternatively
speaking, the body terminal of the transistor M1 which remains to
be turned off when the regulated voltage Vm is considered as the DC
input voltage Vdc_in is electrically connected to whichever of the
supply voltage Vdd and the regulated voltage Vm having the greater
voltage level.
As illustrated above, a modulated power supply circuit including a
supply modulator supplies a modulated voltage Vpa, including an AC
component Vpa_ac and a DC component Vpa_dc, to a power amplifier.
Moreover, a control method of the modulated power supply circuit is
provided. The control method can be summarized to include the
following steps.
Firstly, a supply voltage Vdd is converted to a regulated voltage
Vm by the DC-DC voltage converter. The regulated voltage Vm can be
greater than or less than the supply voltage Vdd. Then, the AC
component of the modulated voltage Vpa_ac is generated by the
linear amplifier according to the regulated voltage Vm and an
envelope tracking signal Venv. The envelope tracking signal Venv
instantaneously tracks amplitude change of the input signal Sin of
the power amplifier. On the other hand, the supply voltage Vdd is
also received by the switching converter. The switching converter
further utilizes one of the supply voltage Vdd and the regulated
voltage Vm as the DC input voltage Vdc_in and converts the DC input
voltage Vdc_in to the DC component of the modulated voltage Vpa_dc.
The switching converter performs a step-down conversion so that the
DC component of the modulated voltage Vpa_dc is less than the DC
input voltage Vdc_in.
As illustrated above, power efficiency and thermal reduction of the
modulated power supply circuit can be improved. Moreover, the
linearity of the power amplifier can be improved, and higher
operation power can be provided by the power amplifier. The
modulated power supply circuit can be used in many portal
applications where efficiency and battery life are paramount.
While the invention has been described by way of example and in
terms of the preferred embodiment(s), it is to be understood that
the invention is not limited thereto. On the contrary, it is
intended to cover various modifications and similar arrangements
and procedures, and the scope of the appended claims therefore
should be accorded the broadest interpretation so as to encompass
all such modifications and similar arrangements and procedures.
* * * * *